The three-part series, which becomes available Monday on the streaming service, ties together two parallel quests that are remarkably straightforward.

Perhaps that’s because the series is based on actual events, which gives the producers fewer options for tacking on TV-friendly subplots and minidramas.

In this case, happily, less is more.

For the central crime plot, Leicestershire Detective David Baker (David Threlfall, top) is investigating the murder of two teenage schoolgirls in the 1980s.

The killings happened three years apart, and Baker is convinced the second was the work of the same killer, emboldened after deciding he was in little danger of being charged with the first.

Baker takes both cases very personally, working with the families and sharing their pain as time passes and there are no explanations, never mind perpetrators.

Meanwhile, a few miles away, Leicester University scientist and researcher Dr. Alec Jeffreys (John Simm, top and left) is working to crack the genetic code that today is universally known as DNA.

Jeffreys is convinced that each human being has a unique genetic code buried deep under the common genes that all Homo sapiens share. He’s also convinced there must be a way to isolate and identify it.

DNA, at its most basic, explains why each person has his or her own combination of eye color, digit length, cheekbone setting and the like.

But that’s not where DNA fits into Code of a Killer. Rather, Code recounts how, when Dr. Jeffreys finally did find a way to isolate DNA identification, these Leicestershire murders became the first recorded case in which DNA was used as legal evidence to identify a perpetrator.

Police today routinely use DNA to identify both guilty and innocent parties. Successful television franchises have been built on the science of DNA. DNA has solved mysteries that lay dormant for centuries.

But in the 1980s, Dr. Jeffreys still had to explain to everyone, including sometimes skeptical police and judges, what DNA really was. That it constituted scientifically irrefutable proof a particular individual was involved in an event because he or she left the DNA fingerprint.

The science drama in Code of a Killer lies largely in watching Jeffreys and his assistant try dozens of lab experiments, failing at all of them yet moving ever closer to the one that would succeed.

It’s a little geeky, even knowing the impact of its success can’t be overstated.

Interestingly, Baker’s police work has some of that same methodical progression. He investigates the old-fashioned way, looking for witnesses and motives and trying to put himself in the mind of the killer while searching relentlessly for some witness who might know something.

Because the first murder was committed in a particularly conducive out-of-the-way area, Baker suspects the killer was a local man.

This makes the fact he’s still on the loose feel more chilling during the hunt. It pays dividends, however, once Baker and Dr. Jeffreys realize they can work together.

Because there’s no such thing as a DNA databank, they must get samples from virtually all the local men.

That wouldn’t work in London. Here, it has a shot.

Code of a Killer lacks some of the flash usually found in TV dramas, even those based on true stories.

The linear nature of the parallel storylines, however, gives it a fresh dimension. An unglamorous portrayal of police and university lab work doesn’t rule out good TV entertainment.